Tab folding and sealing apparatus and method

ABSTRACT

A method and apparatus for folding a tab over a peelable panel on an end structure comprising a ring/panel. The ring and panel are formed from the same flexible material which has no inherent deadfold characteristic. In one embodiment an upper tab fold tool includes a pivotable plate for holding the folded edge of the tab in position prior to heat sealing to the peelable panel.

This Application is the U.S. national phase of International ApplicationNo. PCT/EP2005/54484 filed on Sep. 9, 2005.

TECHNICAL FIELD

This invention relates to tab folding. In particular it relates to anapparatus for folding a tab over a peelable lid structure on acontainer.

BACKGROUND ART

Tabs are in general use for the removal of peelable panels and typicallyare formed from a projection of the panel. By grasping the tab, thepanel can be peeled off a container. The material of the peelable paneland integral tab typically comprises a laminate structure, which mayinclude a heat sealable layer and a barrier layer such as aluminiumand/or varnish. In closures on containers for food products whichrequire processing by retorting, for example, the tab may be folded overthe main part of the panel in order to avoid handling problems. Oftenthe peelable panel is fixed to a metal ring which is then seamed to theedge of a can body. In order to avoid damage to the tab, particularlyduring processing, it is usual to fold the tab radially inwardly awayfrom the ring prior to the seaming operation.

Folding the tab of a peelable panel which includes a thick layer ofaluminium can be carried out in a relatively straightforward manner byusing the material's inherent deadfold properties. A typical foldingprocess for such a tab/panel is carried out in three steps as shown inFIG. 1. Firstly the peelable panel 1 is fixed to a metal ring 2 by heatsealing (FIG. 1( a)). The ring 2 includes a flat annulus 3, an uprightwall 4 and a seaming panel 5. During heat sealing, the tab 6 is forcedby the heat sealing tool 10 around the wall 4 at the side of the ring soas to lie in a position approximately perpendicular to the centre partof the peelable panel. In a second operation, a folding tool 11 passeslaterally over the seaming panel (FIG. 1( b)) until it contacts the taband folds the tab 6 over the annulus 3 of the ring 2 and main part ofpanel 1 (FIG. 1( c)). When the tool 11 is removed, deadfold in thetab/panel material maintains the tab 6 in its folded position (FIG. 1(d)). Finally, a press tool 12 crushes the tab flat against the rest ofthe peelable panel 1 (FIG. 1 (e)).

This prior art folding method is only suitable for material which hasinherent deadfold properties, typically including an aluminium layer ofaround 70 μm (microns) in thickness. In all types and thicknesses oflidding material, the tab has to stay on, or very close to the lid panelto avoid being damaged during handling and/or seaming. With flexiblematerial structures, the lidding may be a three or four layer structureusing less than 30 μm (microns) or at most 40 microns of aluminium,typically 0 to 10 μm. Not only would the tab crush operation of FIG. 1(e) fail to maintain the tab of such flexible lidding structures in thedesired folded position, but flexible tab material adjacent the uprightwall and seaming panel of the ring 2 is free to move and tends towrinkle or to develop a fold in a non-ideal position during the foldingand “crushing” operations (FIGS. 1( d) and (e)), thus risking damage tothe tab.

This invention seeks to provide a method and apparatus for use with endsin which the tab and lid structure are formed from the same flexiblematerial, which has no inherent deadfold characteristic.

DISCLOSURE OF INVENTION

According to the present invention, there is provided an apparatus forfolding a tab of flexible material over a peelable panel, in which thetab and peelable panel are formed from a single piece of the sameflexible material which has no inherent deadfold characteristic andwhich, in use, is fixed to a ring or container body such that the tabextends away from the panel, the apparatus comprising: an upper tab foldtool having two independent and distinct regions comprising: a firstregion for folding the tab; and a second region including a biasingdevice for flattening the folded tab against the peelable panel; a lowertab fold tool; and a heat seal stake; and in which either or both of thefold tools are moveable axially relative to each other for folding thetab against the peelable panel and the heat seal stake is provided inthe upper tab fold tool for bonding the folded tab in its foldedposition.

By combining the tab fold and heat seal stake in a single tool, liddingmaterial with no inherent deadfold can be handled and subjected tosubsequent thermal processing without risk of damaging the tab.

The peelable panel is fixed to a flat annulus of the ring or a containerbody to form the peelable end structure. An upright wall of the ring orcontainer body extends away from the annulus to a seaming panel.Ideally, the biasing device flattens the folded edge of the tab againstthe peelable panel prior to folding the remainder of the tab flatagainst the peelable panel. This prevents the tab from moving and avoidsbonding of the folded tab in a position in which the folded edge extendsbeyond the flat annulus and around the upright wall.

The biasing device may include a pivotable plate which is held againstthe tab fold upper tool by the seaming panel such that lateral movementof the lidding material relative to the apparatus releases the pivotableplate for flattening the folded edge of the tab against the peelablepanel.

Typically the apparatus further comprises a heat seal tool for fixingthe peelable panel to a ring although this tool may alternatively becompletely separate from that for tab folding and heat sealing of thetab.

According to another aspect of the present invention, there is provideda method of folding a tab of flexible material over a peelable panel,the method comprising: providing an upper tab fold tool, a lower tabfold tool and a heat seal stake; moving either or both of the tab foldtools axially relative to each other and folding the tab against thepeelable panel by

a first step of folding the tab; and a second step of flattening thefolded edge of the tab against the panel prior to folding and flatteningthe remainder of the tab flat against the panel; and moving the heatseal stake into contact with the folded tab and bonding the folded tabin its folded position.

Prior to folding and flattening the tab to the panel the method mayfurther comprise fixing the panel to a ring with the unbonded tabextending away from the remainder of the panel and adjacent a seamingpanel of the ring. The method may, in an alternative embodiment,comprise fixing the panel directly to a container with the unbonded tabextending away from the remainder of the panel and adjacent a seamingpanel of the container body.

In a preferred embodiment, the method further comprises providing abiasing plate in the upper tab fold tool; moving the ring/panelstructure and upper tab fold tool relative to each other, a seamingpanel of the ring holding the biasing plate against the upper tab foldtool; moving the ring/panel structure and apparatus relative to eachother, and releasing the biasing plate, flattening the tab edge againstthe panel and bonding the tab onto the peelable panel. Typically, thebiasing plate is pivotable and/or spring loaded.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described withreference to the drawings, in which:

FIG. 1 is the prior art tab folding apparatus described above;

FIG. 2 which is a schematic side view of a first embodiment of apparatusfor tab folding; and

FIG. 3 is a schematic side view of a second embodiment of tab foldingapparatus.

MODE FOR THE INVENTION

In all the embodiments of FIGS. 1 to 3, the peelable panel 1 is fixed toa metal ring 2 by heat sealing. The ring 2 includes a flat annulus 3, anupright wall 4 and a seaming panel 5. During heat sealing, the tab 6 isforced by the heat sealing tool 10 around the wall 4 at the side of thering so as to lie in a position approximately perpendicular to thecentre part of the peelable panel. The end structure of FIGS. 2 and 3has a peelable panel which is formed from flexible material having alaminated structure with 0 to 40 μm (microns) of aluminium and includesa heat sealable material on its outer surface for bonding the tab in itsfolded position.

In a second operation, upper tab fold tool 20 passes laterally over theseaming panel until it contacts the tab 6 and folds the tab over theannulus 3 of the ring 2 and main part of panel 1. However, in contrastwith the prior art of FIG. 1, upper tab fold tool 20 of the presentinvention combines tab fold, crush and heat seal in a single tool 20 foruse with flexible lidding materials.

In the embodiment of FIG. 2, upper tab fold tool 20 comprises a firstportion 21 for folding the tab 6 over the peelable panel 1 (FIG. 2(2)).During relative axial movement of ring/panel and tool 20, a “letterbox”25 is formed between upper tab fold tool 20 and lower tab fold tool 30.As the ring/panel pass laterally through the letterbox 25, portion 21 ofthe upper tab fold tool passes with minimum clearance over the seamingpanel and folds the tab 6 over the peelable panel 1. Minimisingclearance avoids wrinkling of the flexible lidding material or foldingthe tab in a non-ideal position such that the fold is too close to thecountersink wall, resulting in the folded edge extending to the uprightwall.

Central region 22 of the upper tab fold tool 20 maintains the tab in itsfolded position as the ring passes through the letterbox 25. FIG. 2(3)shows two ring/panel structures in folding and crushing positions forclarity only. In reality these operations are carried out with a singlering/panel in the apparatus at any one time.

When the ring/panel structure reached the position at the right handside of FIGS. 2(3) and 2(4), the upper tab fold tool crushes the tab 6and heat seal stake 24 bonds the tab down onto peelable panel 1. Thisoperation may be achieved either by downward movement of the upper tabfold tool, upward movement of the lower tab fold tool (lifting thering/panel structure) as indicated by the arrow in FIG. 2(4), or acombination of these relative movements. Curled edge 7 of the ring 2fits into a recess 31 in lower tab fold tool 30 for crushing and heatsealing.

The upper tab fold tool 20 of the embodiment of FIG. 3 includes a plate40 which is pivotable about point 41 as shown on FIG. 3(3). As thering/panel structure advances through letterbox 25, pivotable plate 40is lifting against the upper tab fold tool 20 by seaming panel 5,against the action of spring 42. Further forward movement releases thepivot plate so that it drops and folds the “edge” 8 of tab 6. This edge8 is thus prevented from movement around the ring 2 and/or up the wall 4of the ring and improves consistency of the folded position of the tab.

In FIG. 3(5), the end is lifted up and the whole tab is folded flat.Heat seal stake 24 bonds the tab in position. Residual heat in thematerial from the initial sealing of the flexible lidding panel to thering may “tack” the tab in place prior to the final heat seal stake. Thetab fold plate 20 also acts as a stripper for removal of the heat sealstake.

The invention has been described above by way of example only andchanges may be made to the method/apparatus within the scope of theinvention. For example, the upper tab fold tool (including such featuresas heat seal stake or pivot plate) may be configured so as to fix tabshaving a variety of profiles. Biasing devices other than spring 40 maybe used.

Although the use of an intermediate ring structure to which the peelablepanel is bonded prior to seaming of the ring to a can body is shown inthe drawings, the invention is applicable to any container which isclosed by a peelable panel with integral tab. For example, the peelablepanel could be on an end or directly attached to the container body.

1. An apparatus for folding a tab of flexible material over a peelablepanel, in which the tab and peelable panel are formed from a singlepiece of the same flexible material which has no inherent deadfoldcharacteristic and which, in use, is fixed to a ring such that the tabextends away from the panel, the apparatus comprising: an upper tab foldtool having two independent and distinct regions comprising: a firstregion for folding the tab; and a second region including a biasingdevice for flattening the folded tab against the peelable panel; a lowertab fold tool; and a heat seal stake; and in which either or both of thefold tools are moveable axially relative to each other for folding thetab against the peelable panel and the heat seal stake is provided inthe upper tab fold tool for bonding the folded tab in its foldedposition.
 2. An apparatus according to claim 1, in which the biasingdevice flattens the folded edge of the tab against the peelable panelprior to folding the remainder of the tab flat against the peelablepanel.
 3. An apparatus according to claim 1 or claim 2, in which thebiasing device includes a pivotable plate which is held against the tabfold upper tool by a seaming panel of the ring such that lateralmovement of the lidding material relative to the apparatus releases thepivotable plate for flattening the folded edge of the tab against thepeelable panel.
 4. An apparatus according to any one of claims 1 to 3,further comprising a heat seal tool for fixing the peelable panel to aring.
 5. The apparatus according to claim 1, wherein the lower tab toolhas a recess adapted to fit a curled edge of a ring/panel structure. 6.A method of folding a tab of flexible material over a peelable panel,the method comprising: providing an upper tab fold tool, a lower tabfold tool and a heat seal stake; providing a biasing plate in the uppertab fold tool for flattening the folded tab against the peelable panel,wherein the peelable panel has no inherent deadfold characteristic;moving either or both of the tab fold tools axially relative to eachother and folding the tab against the peelable panel by: a first step offolding the tab; and a second step of flattening the folded edge of thetab against the panel prior to folding and flattening the remainder ofthe tab flat against the panel; and moving the heat seal stake intocontact with the folded tab and bonding the folded tab in its foldedposition.
 7. A method according to claim 6, further comprising fixingthe panel to a ring or a container body with the unbonded tab extendingaway from the remainder of the panel and adjacent a seaming panel of thering or container body, prior to folding and flattening the tab to thepanel.
 8. A method according to claim 7, further comprising: moving thering/panel structure and upper tab fold tool relative to each other, aseaming panel of the ring holding the biasing plate against the uppertab fold tool; moving the ring/panel structure and apparatus relative toeach other; releasing the biasing plate; flattening the tab edge againstthe panel; and bonding the tab onto the peelable panel.
 9. A methodaccording to claim 8 in which the biasing plate is pivotable and/orspring loaded.
 10. The method of claim 6, wherein the lower tab tool hasa recess adapted to fit a curled edge of the ring/panel structure.